I got a set of nipple wrenches from Mike's XS, item # 35-0109. It has four sizes. 8, 9, 10, 11. I don't think they are metric or sae sizes, just sizes that they are marked. The #8 is the biggest, the #9 fits the nipples on my 75. The #'s 10 and 11 are smaller.
I seem to have misplaced both of my calipers, when I find them I'll measure these wrenches.
Leo